ADHD is a condition marked by symptoms of inattention and hyperactivity/impulsivity persistent over time, present and causing impairment in at least two contexts, such as in the school and at home. However, the degree to which symptoms are present across situations varies from individual to individual. At one end of the spectrum, children may show severe symptoms in several contexts (that is, pervasive ADHD) while others show severe symptoms only in one context (that is, situational ADHD). What underpins the pervasive and situational manifestations is not well understood, and the impact of pervasive and situational dysfunction on future outcome (such as mental health, occupation, and educational status) needs further investigation. Different underlying mechanisms may relate in specific ways to the degree to which ADHD is expressed pervasively or situationally in the school or home setting. In the current study, we focus specifically on the role of executive functioning (that is, goal-directed behavior), emotion processing, and aspects of the family environment, in this matter. We will examine how pervasive and situational ADHD symptoms evolve over time, mapping possible underlying mechanisms, gender differences, and long-term outcome in a large community sample. The findings will have implications for our understanding of the etiology, maintenance, treatment, and prevention of the diagnosis.